1. Field of the Invention
The present disclosure relates to the technology of producing the LTPS products, more specifically, to a method of forming the buffer layer in the LTPS products.
2. Description of the Related Art
The process of forming buffer layer of triple structure in Low Temperature Poly-silicon (“LTPS”, hereinafter) products generally includes the following features:
The metal ions existing on the surface of the glass are mainly metal ions in Group I/II: K, Na, Ca, Mg, Ba and so on.
After the test of SIMS (secondary ion mass spectroscopy), the effect of utilizing the different insulating layer to separate the metal ions are that as follows:
when SiNx is used as the insulating layer, all the metal ions can be effectively separated to less than 1015 by a 500 Å SiNx insulating layer;
when just SiO2 is used as the insulating layer, Ca, Ng, Ba can be effectively separated to less than 1015 by a 800 Å SiO2 insulating layer; however, the effect of separating the K ions and Na ions is poor that a 3000 Å of insulating layer is necessary to separate K ions and Na ions to less than 1015.
Metal ions on the surface of the glass will affect the performance of component devices. Hence, generally, it is necessary to use the insulating layer as the buffer layer for separating the metal ions in positive channel type Thin Film Transistor (“TFT”, hereinafter).
SiNx is not as good as SiO2 when contacting with photoresist/glass, it is easy to peel off. However, the effect of separating metal ions by SiO2 is not as good as SiNx. Hence, presently, the method most widely used is to use the SiO2/SiNx/SiO2 triple structure 6 according to FIG. 1. However, the triple structure will cause the defects of too many layers (which cause poor feature of components), too many processes (which reduces the capacity) and high film thickness (which increases the cost of manufacturing).
A related art has disclosed a method for manufacturing an insulating layer in an MIM (metal-insulator-metal) capacitor, wherein, ethyl orthosilicate and ozone gas are heat reacted on a lower electrode plate of the MIM capacitor to form a silicon dioxide insulating layer. With the adoption of the method, a silicon dioxide insulator is manufactured by a deposition method without containing plasma auxiliary enhancement on a lower metal pole plate of the MIM capacitor manufactured by the conventional method, an upper metal pole plate of the MIM capacitor is continuously manufactured by the conventional method after the insulator is formed, and finally the MIM capacitor is formed. In the method, the preparation method is simplified, and the MIM capacitor adopting the insulating layer has higher performances on breakdown voltage, leakage current, and the like.
Another related art uses the process of Al thin film deposition, linkage, ion implantation and bonding heat treatment to prepare the substrate in SOI structure with the buried layer of two or the multiple layer chosen from aluminum nitride, alumina, or AIN, Al2O3, Si3N4 or SiO2. The manufacturing steps are that as follows: depositing Al thin film on the wafer; realizing the transfusion of the layer by the linkage process; forming the buried layer by N ions or O ions implantation.
Another related art has disclosed a buffer layer and method of forming the buffer layer, the method including forming a high-k dielectric layer; forming a titanium nitride layer over the high-k dielectric layer; forming a silicon layer on the titanium nitride layer; annealing the silicon layer in the titanium nitride layer to form an annealed silicon layer and forming an n-metal over the high-k dielectric layer. Consequently, it did not solve the problem of the cross contamination in LTPS.